Intumescent coated crosslinked polyolefins

ABSTRACT

Articles of manufacture are described comprising crosslinked polyolefins having intumescent coatings thereon. Said articles are self supporting and substantially retain the shape of the original articles even after exposure to pryolysis and/or combustion temperatures of up to 2,500* F.

United States Patent 1191 Rees et a1. June 28, 19 74 [54] INTUMESCENT COATED CROSSLINKED 3,973,243) gcclitt et a1 .l [/38 Q ,135, 1 u mer 88 POLYOLEFINS 3,214,422 10/1965 Mageli et a1. 260/610 R 17 n n o L- r 3,284,216 11/1966 Kaplan 117/ 37 x George E. Williams, Brighton, Mich. 3,322,612 5/1967 Burd 117/137 X 3,422,048 1/1969 Cannelongo 117/136 X [73] Asslgneeggg g gg gig cmnpany 3,627,728 12/1971 Fernandes 61.611 260/949 GA 1221 ile M y 30 972 Prim/try Exam/287 111611661 6616616668 [21] APP] 257,873 Assistant Examiner-Harry J. Gwinnell [52] US. Cl 117/137, 117/9 5, 117/136, [57] ABSTRACT 117/138.8 E, 220/64, 220/88 R 1 51 1111. C1 B32b 27/32, C09d 5/18 f of manufacm'e iescnbed compremgr [58] Field of Search 1 17/138 8 E 136 137 crosslmked polyolefins havmg mtumescent coatings 117/138 9 GA 220/88 6 thereon. Said articles are self supporting and substantia11y retain the shape of the original articleseven after [56] References Cited exposure to pryolysis and/orcombnstion temperatures UNITED STATES PATENTS of up to 2500 1 2,676,162 4/1954 Marotta 117/137 X 8 Claims, N0 Drawings INTUMESCENT COATED CROSSLINKED POLYOLEFINS This invention relates to articles of manufacture comprising crosslinked polyolefins having intumescent coatings.

The use of intumescent coatings to protect flammable substrates is well known in the art. However, attempts to use intumescent coatings to protect polyolefin substrates heretofore have been unsuccessful since the polyolefin substrates heretofore employed have failed to provide an adequate support for an intumescent coating at temperatures of about 25 F or higher. This characteristic ihadequacy of polyolefin substrates to provide a suitable support for intumescent coating at elevated temperatures has restricted the use of polyolefins in combination with intumescent coatings as a convenient and/or economical means of manufacturing intumescent coated self supporting flame retardant polyolefin articles.

It is an object of this invention to provide intumescent coated polyolefin articles wherein the polyolefin substrate is self supporting and provides a suitable sub strate base for an intumescent coating at temperatures above about 250 F. Another object is to provide self supporting flame retardant articles of manufacture comprising extruded, thermoformed, blow-molded, injection molded, or rotationally molded polyolefin articles having an intumescent coating applied thereto. These and other objects will be apparent from the written description and the appended claims.

in accordance with this invention a new and improved article of manufacture is provided comprising a cross-linked polyolefin wherein at least a portion of said polyolefin has an intumescent coating.

The cross-linked polyolefins that can be employed in the practice of this invention can be prepared by cross linking a polyolefin selected from ethylene homopolymers, copolymers of ethylene and at least one acrclic l-monoolefin having from three to eight carbon atoms per molecule, and mixtures thereof, wherein the uncross-linked polyolefin is characterized by a density range of from about 0.940 to0.970 as determined by ASTM D 1505-68.

Suitable cross-linking agents that can be employed to form the crosslinked polyolefin comprises any peroxy compound which under suitable crosslinking. process conditions will provide a cross-linked polyolefin having a density within the range of from about 0.930 to about 0.940. Preferred cross-linking agents are acetylenic diperoxy compounds which have molecular weights within the range of from about 230 to about 550 that can be represented by the formula:

lected from methyl and ethyl radicals. Further illustrative of suitable peroxy compounds are the following specific chemicals: 2,7-dimethyl-2,7-di(tbutylperoxy)octadiyne-3,5,3,6-dimethyl-3,6(t-butylperoxy)octyne-4, 2,5-dimethyl-2,5-di(peroxy-n-propyl,

the practice of this invention include any suitable intuv mescent composition which, on heating, forms large amounts of incombustible, or nearly so, residue while at the same time forms a cellular foam with good insulating properties. Representative intumescent coatings which are generally useful comprise compositions that contain (a) sources of carbonaceous materials suitable for char formation, such as sugars, polyhydric alcohols, polyhydric phenols, starches, and the like, (b) dehydrating agents such as ammonium phosphates, amine phosphates, phosphate esters, and borates, and c) blowing agents such as dicyandiamide, melamine, guanidine, glycine, urea, chlorinated paraffin percent chlorine) and the like. Other materials can be added to the coatings to improve toughness of the carbon foams such as aminoplasts, i.e., urea-or melamineformaldehyde resins, which are believed to form a tough skin over the cellular foam. Preferred intumescent coatings comprise latex base coatings.

The cross-linked polyolefin compositions employed in the practice of this invention can be prepared by forming or shapingadmixtures of cross-linking agent and uncross-linked polyolefin in suitable proportions at suitable temperatures and pressures to form acrosslinked polyolefin as stated hereinbefore having a density of about 0.930 to about 0.940. Since the amount of cross-linking agent employed in any given process will depend upon the. mass, size, shape, etc., of the object being formed as well as the time and temperatures employed during cross-linking of the polyolefin, the proportions of cross-linking agent to polyolefin can vary widely, however preferably at least 0.1 part up to about 10 parts of acetylenic diperoxy compound is employed per parts of uncross-linked polyolefin. In general, the cross-linking temperatures that can be employed vary widely, however suitable cross-linking temperatures generally are within the range of from about 250 F to about 650 F. The cross-linking time period can vary widely, however generally suitable time periods are within the range of from about 1/10 of a second up to 5 hours.

Any amount of intumescent coating can be applied to the cross-linked polyolefin substrate in accordance with this invention. In general, an intumescent coating within a range of from about I to 1,000 mils of intumescent coating per inch of thickness of cross-linked polyolefin substrate provides'stifficient intumescent mate rial to protect the cross-linked polyolefin substrate from the direct pyrolysis and/or combustion products of a gas flame temperature in the range of from about 2,000 to 2,500 F for a period of 5 minutes. In general the intumescent coating should be a contiguous and continuous coating.

- In general the intumescent coated cross-linked polyolefins of this invention, when employed in the form of sheets, films, tubes, containers, fibers, filaments, and the like, are effective in controlling and containing the 3 4 pyrolysis and combustion products commonly assotumescent-coated and intumescent-coated cross-linked ciated with such items as burning wood, paper, textiles, polyolefin substrates to initially support combustion for plastics, polymers, and the like. a period of five seconds or more continuously in the ab- Set out hereafter are examples which illustrate the sence of an open flame. practice of this invention. 5 I V I EXAMPLEl TABLE H A series of runs was carried out to determine the abil- Open Flame Test Results cmminked polyolefins ity of both uncross-iinked and cross-linked polyolefin substrates having intumescent coatings to remain self- 1 2 supporting while the intumescent coating was in direct Pol: olefin progemes contact with an open flame. The intumescent coated Density in grams per cc 930-933 930-933 polyolefin compositions were evaluated according to g i rystalline Melting Point, Indeterminate Indeterminate the following procedure. Samples one-eighth inch "F thick, five inches square, of both uncross-linked and e t q No Yes cross-linked polyolefin compositions having one side Average m semnds 270 intumescent coated were individually supported on a "As d fin d heminberm i Tabl i,

four and one-half inch diameter ring located seven inches above a Fisher 120-21 burner having a 1 /2 inch diameter grid. A flame extending upwardly to the in- EXAM? H tumescent-coated surface was adjusted so that the tip A Serles of tests e arr ed out to determine the f th fl j t t h d th i t t ti ability of noncr'oss-linked and cross-linked polyolefin th opposite id from th atin 3 1% i h di t intumescent coated containers to contain the combushemispherical steel ball weighing approximately 130 tion and pyrolysis products of burning paper. Identical grams was suspended directly above the vertical axis of containers having no intumescent coatings were used the gas flame. Both the gas flame and the steel ball were for Control purposes. he polyolefin containers were positioned directly in the middle of the sample under ma n a McNeil 20032 Rotational Molding Matest. The approximately 5 mil thick intumescent coated chine charged with 400 grams of cross-linked polyethsurfaces of all samples were continuously exposed to a y e a 5 Overt mp r r heated for l mingas flame at a flame burst temperature of 2,500 F. utes, followed by 2 minutes of fog spray and 2 minutes Each run consisted of three samples exposed to the of 82 F Water cascade. After molding the top was cut flame. The average time required for the 1% inch diamt, forming an open top container which weighed apeter ball to pass completely through the three noninproximately 290 grams. All the containers were similar tumescent-coated and the three intumescent-coated in SiZe,' inches h g 7 inches in diameter, With a Wall r li k d l l fi a l s wa r rd d, Th thickness of about 0.65 inch. Each container was filled results of said tests are set out in Table l hereafter. h newspaper. hich was ignited, and allowed to TABLE'i Open Flame Test Results Uncross linked Polyolefins Run No. l 2 3 4 olyolefin Properties Density in grams per cc .955 .955 .955 .955 Vicat Softening Point. F

(ASTM D l525-65T) 200 200 200 200 Crystalline Melting Point, "F 250 250 250 250 Melt Index (ASTM l238-65T) l8 18 6.5 6.5 lntumescent Coatings No Yes No Yes Average Time in seconds 79 83 74 106 "'A solvent based modified vinyl coating containing carbonaceous materials and a foaming agent which reacts to flame or heat at 300F (Alhi Mfg. Co. Coating I07A).

No measurable surface penetration by the 130 gram burn uninterruptcdly until all the newspaper had been steel ball occurred during exposure of the intumescentconsumed in a combustion process at a temperature of coated cross-linked polyolefin substrates to flame burst about 450 F. The temperatures of the tests correlated temperatures of 2,500 F. The average time in seco d with the particular polyolefin employed and the results defined in Table II is the time required for the noninare ulated in T l "1 her after- TABLE III Open Flame Test Results Cross-linked Polvolefins 3 4 Polyolefin Properties lntumescent Coating No Yes No Yes Remarks Container Container Container Container softened. softened and bottom exhibited collapsed slumped badly burned, minor and exposing melted and distortion completely uncoated stuck to with no burned up. areas to the concrete slumping of t open flame test surfacev the container which theresides. after ignited and completely burned.

"As defined hereinhefore in Table I.

As illustrated by the above examples, intumescent coated cross-linked polyethylene articles, in the form of containers, such as waste baskets, are self supporting as well as resistant to pyrolysis and/or combustion temperatures within a temperature range of from 450 to 2,500 F.

Further modifications of the teachings of this invention employing cross-linked polyethyleneand intumescent coating as articles of manufacture will be apparent to those skilled in this art.

What is claimed is:

1. An article of manufacture formed of a polyolefin selected from the group consisting of ethylene homopolymers, copolymers of ethylene and at least one acyclic l-monoolefin hydrocarbon having three to eight carbon atoms per molecule, and mixtures thereof, wherein said polyolefin has been cross-linked with a suitable cross-linking compound, and wherein at least a portion of said article has an intumescent coating thereon.

2. An article according to claim 1 wherein the crosslinked polyoletin is characterized by a density within the range of from about 0.930 to about 0.940. and

' wherein the cross-linked polyethylene substrate contigwithin the range of from about 230 to about 550 and is represented by the formula:

wherein each R is the same or different and is independently selected from the group consisting of tertiary alkyl, alkyl carbonate and alkyl benzoate radicals, and each R is the same or different and is independently selected from the group consisting of methyl and ethyl radicals.

5. An article according to claim 4 wherein said article retains substantially the original article form after said coating has been subjected to pyrolysis or combustion temperatures up to 2,500 F. 

2. An article according to claim 1 wherein the cross-linked polyolefin is characterized by a density within the range of from about 0.930 to about 0.940, and wherein the cross-linked polyethylene substrate contiguous to said coating retains substantially the original substrate form after said coating has been subjected to direct pyrolysis or combustion at temperatures up to 2,500* F.
 3. An article according to claim 2 wherein said cross-linked polyolefin is prepared by contacting an uncross-linked polyolefin characterized by a density within the range of from about 0.940 to 0.970 with an acetylenic diperoxy compound under suitable cross-linking temperatures and pressures.
 4. An article according to claim 3 wherein said acetylenic diperoxy compound has a molecular weight within the range of from about 230 to about 550 and is represented by the formula:
 5. An article according to claim 4 wherein said article retains substantially the original article form after said coating has been subjected to pyrolysis or combustion temperatures up to 2, 500* F.
 6. An article according to claim 5 wherein said article contains a cavity and the entire wall of said cavity is covered with said intumescent coating.
 7. An article according to claim 6 wherein said intumescent coating comprises caRbonaceous materials, dehydrating agents, blowing agents, and said coatings react to flame or heat at temperatures of about 300* F.
 8. An article according to claim 7 wherein said article is a waste paper basket container. 